The invention concerns a device for counting and determining the direction of passage of living beings. It finds its application in the field of counting and determining the direction of passage of persons on paths or in buildings. However, it can also apply to the counting and determination of the direction of passage of animals on paths.
FIG. 1 depicts a device for determining the direction of passage 100 of a living being 114 of the prior art, which comprises a pyroelectric cell 102 and a processing unit (not shown).
The pyroelectric cell 102 is of the type comprising a first detection window 104 and a second detection window 106 disposed, horizontally, alongside each other. The pyroelectric cell 102 and in particular the first detection window 104 and the second detection window 106 are sensitive to infrared radiation, and the pyroelectric cell 102 delivers an electrical signal 200 representing the passage of the living being 114 in front of the detection windows 104 and 106. The electrical signal 200 is shown in FIG. 2a. 
The processing unit is connected to the pyroelectric cell 102 and receives the electrical signal 200 thus delivered and, from the analysis of this electrical signal 200, it determines the direction of passage of the living being 114 in front of the device for determining the direction of passage 100.
The parallelepipeds 110 and 112 of FIG. 1 represent the zones of influence of the detection windows 104 and 106. That is to say infrared radiation emitted inside the first zone of influence 110 is perceived by the first detection window 104 and infrared radiation emitted inside the second zone of influence 112 is perceived by the second detection window 106.
The arrow 116 represents the direction of passage of the living being 114.
The electrical signal 200 represents the electrical signal delivered by the pyroelectric cell 102 during the passage of the living being 114 in front of the pyroelectric cell 102. The arrow 210a represents the direction of passage of the living being 114. In the example in FIG. 2a, the arrow 210a repeats the direction of the arrow 116 in FIG. 1.
The maximum 202 represents the detection by the first detection window 104 of the passage of the living being 114 and the minimum 204 represents the detection by the second detection window 106 of the passage of the living being 114. The secondary minimum 206 and the secondary maximum 208 represent the damping of the signal and depend on the elements making up the pyroelectric cell 102 and the processing unit.
If the living being 114 moves in a direction opposite to that of the arrow 116, the electrical signal 200 is reversed, that is to say the signal passes first of all through the minimum 204 representing the passage of the living being 114 in front of the second detection window 106 and then a maximum 202 representing the passage of the living being 114 in front of the first detection window 104. Such an electrical signal is depicted at FIG. 2b. The direction of passage of the living being 114 is then represented by the arrow 210b. 
The determination of the direction of passage of the living being 114 in front of the device for determining the direction of passage 100 therefore seems to be able to take place by analysis of the electrical signal 200.
The problem with the device 100 of the prior art is that in fact, this determination is accurate only if the temperature of the living being 114 is greater than that of the device for determining the direction of passage 100.
This is because, if the temperature of the living being 114 is lower than that of the device for determining the direction of passage 100, the curves in FIGS. 2a and 2b are reversed and there is then a lack of determination of the direction of passage of the living being 114.
Thus, because of the reversal of the difference in temperature between the living being 114 and the device for determining the direction of passage 100, there arises uncertainty with regard to the direction of passage of the living being 114 in front of the device for determining the direction of passage 100. Such a reversal in the difference in temperature may exist when the device for determining the direction of passage 100 is placed in a heated corridor and the living being 114 comes from a place where the temperature is lower, for example outside, and his garments are cold.
In addition, such a device for determining the direction of passage 100 does not make it possible to count the number of living beings 114 passing in front of it.